Formal:
* Dziękuję za przybycie. (dee-KYOO-n-yay za pri-BEE-tsee-eh) - This is the most formal and polite way to say it.
* Dziękuję za przyjście. (dee-KYOO-n-yay za pshee-SHEN-tsee-eh) - This is also formal, but slightly less stiff than "dziękuję za przybycie".
Informal:
* Dzięki za przyjście. (DZEN-kee za pshee-SHEN-tsee-eh) - This is the most casual and common way to say it.
* Dziękuję za przyjście, miło Cię widzieć. (dee-KYOO-n-yay za pshee-SHEN-tsee-eh, mee-loh TSEE-eh vee-dzee-etch) - This is a more personal and friendly way to say "thank you for coming, it's nice to see you".
Note: In Polish, it's common to use the masculine form of "you" (pan/pani) when speaking to someone formally, even if they are female.
For example:
* Dziękuję Panu/Pani za przybycie. (dee-KYOO-n-yay PA-noo/PA-nee za pri-BEE-tsee-eh) - "Thank you for coming, sir/madam."